Architectural Tailoring and Reinforcement Strategies for Improved Bearing Strength in Thick Carbon Fiber/Epoxy Laminates

ABSTRACT

This study provides a unified experimental comparison of 11 joint configurations in thick (7–12 mm) vacuum‐infused CFRP laminates, addressing a gap where individual reinforcement strategies have been studied in isolation but never benchmarked head‐to‐head under identical conditions. Layup architecture variants (baseline quasi‐isotropic, hard QI, soft QI, Double–Double), local reinforcement strategies (tow steering, concentric random mat tapering, random mat surface layers, metallic bushings), and hybrid or through‐thickness architectures (FiberJoints metallic–fiber patches, quadriaxial fabric, 3D woven angle‐interlock preforms). Double‐shear tests following ASTM D5961 were complemented by pulsed thermography and optical microscopy. The Hard QI + Taper configuration delivered the highest specific initial bearing load (196 kN/kg), followed by FiberJoints (181 kN/kg) and tow‐steered QI (161 kN/kg)—a 24%–50% improvement over baseline QI (130 kN/kg). FiberJoints provides independent validation of the Jakobsen et al. hybrid patch concept in a thick VARI laminate system. Quadriaxial laminates, though lower in specific initial strength (143 kN/kg), delivered record energy absorption (≈1140 J). Soft QI and Double–Double underperformed due to premature failure. Thermography discriminated between bearing‐, net‐tension‐, and shear‐out‐dominated failure mechanisms. These results establish quantitative benchmarks for reinforcement strategy selection in thick CFRP bolted joints.